Massive computer networks, ready access to such communications by consumers and businesses alike, and the prevalence of personal computing devices have made access to multimedia documents widespread. Computers supporting graphical user interfaces and audio have made web pages incorporating multi-media content a common form of document and web pages represent a common interface for computer programs. Gigantic numbers of online multimedia documents constitute a massive amount of content accessible to hundreds of millions of users. Currently however, as is well understood by those skilled in the art, whilst the user may view such online documents, and thereby passively consume such content, the user's ability to actively engage with such content is extremely limited. There has been a trend for site publishers to encourage user engagement by such means as blogs, forums and bulletin boards and such means have indeed resulting in a massive explosion of user generated content but such attempts to go beyond the passive consumption of packaged content do not represent a powerful general model for interaction with content because the user's ability to comment on content in such cases is limited, typically constrained to features provided by the web site implementation and authorised by the website publisher. Such limitations dictate which content can be commented on at what time and in what way. The general definition of ‘annotation’ is extra information associated with a particular point in a document and hence we note that such limited user interaction with online content constitutes a weak form of annotation—the forms of extra information are limited, the points that may be annotated are limited, and the documents that may be annotated are limited.